Tomaymycin is a naturally occurring antibiotic having, besides its anti-bacterial effectiveness, cytotoxic and antitumor activity. Tomaymycin belongs to the chemical group of pyrrolobenzodiazepines (PBD), which are monomeric compounds with weak antibiotic properties that specifically alkylate the minor groove of DNA at a 5′-Pu-G-Pu base sequence. Tomaymycin was isolated from the culture filtrate of Streptomyces achromogenes var. tomaymyceticus by K. Arima (Arima et al., 1972; Nishioka et al., 1972). It was found that tomaymycin is synthesized by a series of proteins that are encoded by a set of genes clustered within a gene cluster. The biosynthetic gene cluster for tomaymycin has been elucidated by Li et al. (Li et al., 2009). Tomaymycin has proven active against tumours in mice, such as sarcoma 180; the benzpyrene sarcoma; the mamma tumor; or leukosarcomatosis such as leukosarcomatosis AKR or C1498 or against leukemia, plasmacytoma and ovarian cancer cell lines. Tomaymycin has the structural formula presented in FIG. 1(A). 11-de-O-methyltomaymycin has the empirical formula C15H18N2O4 and a molecular weight of 290.32. The structural formula of 11-de-O-methyltomaymycin is shown in FIG. 1(B). The tomaymycin-urea adduct is shown in FIG. 1(C).
Whereas 11-de-O-methyltomaymycin is produced during natural biosynthesis, tomaymycin is produced artificially therefrom by addition of methanol during the isolation/purification process (cf. FIG. 1).
FR 1.516.743 discloses a method for the production of tomaymycin using chromatography of a solution comprising the antibiotic adsorbed to an adsorbens, countercurrent distribution, preparation of a complex with urea and regeneration of the antibiotic from the medium comprising the complex. The medium for culturing the strain producing tomaymycin contained usual nutrients, such as an assimilable carbon and nitrogen sources, minerals and optionally growth factors. Assimilable nitrogen sources comprise, for example, nitrate, anorganic or organic ammonium salts, urea or amino acids or substances comprising nitrogen in protidic form, such as casein, soybean flour or distillers' solubles. However, none of the media indicated in FR 1.516.743 resulted in the production of high, satisfactory yields of tomaymycin.
Therefore, there is a need in the art for a method for producing high amounts of tomaymycin. This problem is solved by the present invention.